The volkswagen Type 1, better known as the Beetle, enjoyed the longest manufacturing run of any motor car. Conceived in the 1930s by Dr Ferdinand Porsche and unveiled in 1938, the Käfer, Kever or Coccinelle (it had almost as many nicknames as the countries it was sold in) went into full production after World War II, with over 21 million built in VW factories worldwide, before the last one rolled off the line at Puebla, Mexico in 2003.That longevity must be in the blood of its descendent, the Porsche 911, for this most iconic car, designed by the Austrian engineer's grandson Ferdinand Alexander and shares a similar rear-engine layout, turns 50 this year.Introduced in 1963 as a successor to the Porsche 356 — itself a direct development of the VW — the 911 was conceived as a sports car that could be driven with ease as daily in-town transport and on weekend excursions to the racetrack. In both these objectives it succeeded beyond its creators' wildest dreams.Early production examples came with an air-cooled, two-litre, horizontally opposed six-cylinder engine that produced just 128bhp and powered to a maximum of 210km/h — figures matched and often bettered by many of today's family runabouts.But since then, the neunelfer has evolved into one of the fastest, most capable road machines, a car that, in spite of a layout and body shape from more than half a century ago, could hardly be more contemporary or desirable. The latest GT3 version, for example, qualifies as a bona fide supercar, hiding a normally aspirated, water-cooled 3.8-litre motor beneath its tail that propels it to 100km/h in just 3.5 seconds, and to a maximum speed of almost 320. And there's an even more powerful new 911 Turbo on the way, launched just last month.No wonder, then, that over the years this Porsche has achieved classic status — rare for a machine still in production — widely acclaimed as one of the greatest automobiles made and the yardstick for judging other supercars. It's built in higher numbers than any other luxury sports car, with production now approaching 850,000, and possibly exceeding a million.The 911 and its many derivatives have scored countless successes in racing and rallying, winning blue-ribbon events such as Le Mans (several times with the 935, 936 and 911 GT1 variants), the Monte Carlo Rally (911) and the Paris-Algiers-Dakar raid (911 and 959). It also became one of the most visible success symbols in the 1980s.Naturally, Porsche is doing more to mark its remarkable milestone. The semi-centennial celebrations began in February with a 3,000sq-ft retrospective at the Retromobile Salon in Paris. From now to the end of September, Stuttgart's Porsche Museum is staging a 50 Years of the Porsche 911 exhibition, featuring a host of cars from its copious collection. We can even expect the launch of a 50th-anniversary edition of the 911's current iteration some time in 2013.Porsche has also invited writers to Germany to experience all seven generations of the 911. Which explains why I'm at the test circuit of its Leipzig assembly plant, home to the Panamera and Cayenne. In fact, I've just negotiated a short off-road assault course in a Cayenne, and now have a choice of wheels lined up to take to the track — the aforementioned SUV, a pair of 911 Carreras, a Boxster and a Panamera. For the first few laps, I'm taken on the Cayenne (which, as it's a Turbo S with a thumping 550bhp V8 beneath the bonnet, isn't half the liability it sounds), but eventually — with a couple of stints in the Boxster S — I'm buckling myself into the driver's seat of the Carrera coupe, a seventh-generation 911.Though it looks a little different from the older 911 (also referred to as the 997), this latest version is actually an entirely new car, being slightly bigger, lower and marginally lighter. The entry-level power unit has been downsized to 3.4 litres, which nonetheless delivers a lusty 345bhp (the S model gets a 3.8-litre boxer with 50bhp more) that's as much power as any normal human being would need with a car like this.I press the starter and the flat six bursts to life — a sound so unique that Porsche should consider copyrighting it. I gun it onto the circuit, flipping up through the seven-speed, dual-clutch semi-autobox (a full manual is also available). I'm struck by how the car handles just as precisely and predictably as the Boxster. It's perfectly controlled and firmly planted on the road — I can hardly believe the engine is slung out over the rear axle, as for all 911s since the outset. The engine howls up and down the rev range as it trips about with the astonishing agility of its younger, lighter mid-engine sibling.The steering is now electromagnetic (power assistance is provided by an electric motor), and though that means some reduction in feel, there's more than ample compensation in the car's superb chassis and exquisite balance. Add the brilliant power train that serves up vast helpings of urge and torque, and I climb out convinced this is the most complete 911 ever.The short drive brought the 911 story up to date, but I still need to travel back to its beginnings in Geneva, where I'm attending the city's annual auto show, at which the fifth-generation GT3 is being launched this year. With its specially built, naturally aspirated engine that develops a remarkable 475bhp, this semi-race car represents yet another leap into the future for this evidently ageless Porsche.But my final destination is Stuttgart's Swabian city, one of the world's automotive powerhouses, being home to Mercedes-Benz and Porsche. The latter's base in the northern suburb of Zuffenhausen is also the location of the Porsche Museum where we've gathered. Outside sits two long lines of 911s from the 1960s to the present and we have the opportunity to experience them.Each of us is assigned a car — mine is a white, second-generation 3.2-litre 911 Carrera Clubsport, one of 340 lightweight, race-ready specials built in 1986. Shorn of 100kg compared with the standard car, this stripped-down Clubsport must be the 911 at its most elemental.Although its engine produces just 231bhp, the car weighs less than 1.2 tonnes, a power-to-weight ratio that promises livelier performance than the figures suggest. There is little in the way of sound damping, so the rasp of the overhead-cam, air-cooled engine and the characteristic whirr of the cooling fan fill the cockpit. There's no aircon -— just a simple heater — no electric windows and the steering wheel needs a hefty pull at low speeds. Likewise the clutch is heavy, the stick-shifter for the five-speed box isn't always cooperative and the suspension firm-to-bone-rattling. But once we're underway, the effect is electrifying, the steering is quick and direct, and the car appears almost to vibrate with pent-up energy. Halfway to the Porsche facility at Weissach, I'm seated in a silver 996 coupe. It's the first of the four-valve, water-cooled 911s — the first in the line not to share a single major component with earlier models — and is the key link between old and new. With 294bhp and a 3.4-litre engine, it's considerably more potent than the Clubsport, and also more luxurious and relaxed — though mercifully never sedate.We arrive at the legendary research and development centre. I look around in vain for something to spy on — perhaps the next-generation 911, a new Le Mans car or even the rumoured Formula 1 engine that may be under development. Instead we're led out to lunch beside the test track and the chance to drive as many cars as we can.I make a beeline for the Clubsport. Looking for an earlier set of wheels, I grab an orange 1975 Carrera 2.7, which is so beguiling I greedily hang on to it for several sessions. There's a lovely 996 convertible that reveals the beating heart of a racer. Then there's the gorgeous red 3.2 Speedster, one of the last of the G-series 911s, and the pretty 993 Targa, the first 911 to boast a glass roof that elegantly retracts in front of the rear window — though I have to admit I'm less than enamoured by the four-speed Tiptronic transmission, which could do with at least one extra ratio. This could go on forever and I'm fervently hoping it does, but then someone's called time: There's a plane to catch at 6.30pm, we have to get back to Zuffenhausen — and from there to the airport, the roads are nose-to-tail. We pile back into the Porsches and tear off back to town in a noisy and exuberant high-speed convoy.And as I'm racing across the patchwork of fields and forests on this unexpectedly warm spring afternoon, the car responding immediately to the merest inputs to the wheel, throttle and brakes, I'm reminded why I love to drive, why the 911 is the sports car incarnate — and why this unlikely offspring of the Beetle-turned-supercar could legitimately claim to be the greatest ever.